Establishing trace element concentrations for lichens and bryophytes in the ring of fire region of the Hudson Bay Lowlands, Ontario, Canada.

Peatlands dominate the landscape of the Hudson Bay Lowlands in Ontario, Canada. Recently, mineral deposits of chromium (Cr), nickel (Ni), and copper (Cu) were discovered in the region and anticipated future industrial mining operations have the potential to impact the environment. Lichens and bryophytes are considered excellent biomonitors and indicators of deposition, deriving their nutrients directly from the atmosphere. Trace element concentrations in lichens and bryophytes have not been reported in the Hudson Bay Lowlands. Here, we seek to determine the baseline trace element concentrations of six non-vascular species (Evernia mesomorpha, Bryoria spp., Cladonia stellaris, Cladonia stygia, Sphagnum fuscum, and Sphagnum capillifolium) common to the region, explore linear relationships of trace elements with iron (Fe) as a signature of particulates with geogenic origin, and calculate trace element enrichment factors. Thalli, foliage, and peat (0-30 cm) were collected from 55 locations between 2013 and 2018 and analyzed for trace elements. Thalli and foliar concentrations are among the lowest reported in the broader literature and differ substantially from peat. Fe concentrations were significantly correlated (Pearson's r ≥ 0.8) with aluminum (Al), titanium (Ti), and vanadium (V) in all six species. Enrichment factors show some anthropogenic deposition effects non-vascular organism chemistry. Most trace element concentrations in lichens and bryophytes are indicative of long-range atmospheric transport of dust, but some is attributed to industry, with only minimal inclusions from the local area. Epiphytic lichens are well suited for ongoing atmospheric biomonitoring as industrialization commences.

Fate and budget of poly- and perfluoroalkyl substances in three common garden plants after experimental additions with contaminated river water.

Poly- and perfluoroalkyl substances (PFAS) have become ubiquitous contaminants in the environment. Contamination of the terrestrial ecosystem can occur from the release of aqueous film forming foams (AFFF) used in firefighting operations. Following soil contamination with AFFF, studies report root uptake and translocation of PFAS to other plant organs, typically favouring the short chain moiety. This body of experimental work often focuses on edible organs and generally lacks entire PFAS budgets. Here, we calculate short chain (≤6 carbons) and long chain (≥6 or ≥ 7 carbons) PFAS concentrations and respective budgets for terrestrial multimedia mesocosms (plants, soil and lysimeter) of three common agricultural plants (tomato, lettuce and beet) following irrigation with low level PFAS (<1 µg L-1) contaminated river water (short chain: 167 ng L-1; long chain 526 ng L-1). Total net recoveries were strong, ranging between 91% and 118% of added PFAS across all media. While soil was the largest receptor of PFAS in general (∼70% and 115%), there was considerable mobility to various media, including vegetation (∼3% and 20%) and leachate (∼1%). Translocation of short chain PFAS to tomato flowers resulted with biomagnified concentrations (maximus >4000 ng g-1) and accounted for 1.4% of PFAS additions. While smaller tomato fruits had higher concentrations of short chain PFAS, larger fruit had more total PFAS mass. This work provides a detailed description of the fate of short and long chain PFAS when added to relatively uncontaminated terrestrial agricultural systems. We show low-level PFAS concentrations from real-world irrigation sources can affect various receptors across the multimedia landscape. This is most evident in tomato flowers and fruit where biomagnification and high total masses of short chain PFAS occurred which could have implications for pollinators and consumption, respectively.

Implementation of a Charge-Sensitive Amplifier without a Feedback Resistor for Charge Detection Mass Spectrometry Reduces Noise and Enables Detection of Individual Ions Carrying a Single Charge.

Charge detection mass spectrometry (CDMS) depends on the measurement of the charge induced on a cylinder by individual ions by means of a charge-sensitive amplifier. Electrical noise limits the accuracy of the charge measurement and the smallest charge that can be detected. Thermal noise in the feedback resistor is a major source of electrical noise. We describe the implementation of a charge-sensitive amplifier without a feedback resistor. The design has significantly reduced 1/f noise facilitating the detection of high m/z ions and substantially reducing the measurement time required to achieve almost perfect charge accuracy. With the new design we have been able to detect individual ions carrying a single charge. This is an important milestone in the development of CDMS.

Higher Resolution Charge Detection Mass Spectrometry.

Charge detection mass spectrometry is a single particle technique where the masses of individual ions are determined from simultaneous measurements of each ion's m/z ratio and charge. The ions pass through a conducting cylinder, and the charge induced on the cylinder is detected. The cylinder is usually placed inside an electrostatic linear ion trap so that the ions oscillate back and forth through the cylinder. The resulting time domain signal is analyzed by fast Fourier transformation; the oscillation frequency yields the m/z, and the charge is determined from the magnitudes. The mass resolving power depends on the uncertainties in both quantities. In previous work, the mass resolving power was modest, around 30-40. In this work we report around an order of magnitude improvement. The improvement was achieved by coupling high-accuracy charge measurements (obtained with dynamic calibration) with higher resolution m/z measurements. The performance was benchmarked by monitoring the assembly of the hepatitis B virus (HBV) capsid. The HBV capsid assembly reaction can result in a heterogeneous mixture of intermediates extending from the capsid protein dimer to the icosahedral T = 4 capsid with 120 dimers. Intermediates of all possible sizes were resolved, as well as some overgrown species. Despite the improved mass resolving power, the measured peak widths are still dominated by instrumental resolution. Heterogeneity makes only a small contribution. Resonances were observed in some of the m/z spectra. They result from ions with different masses and charges having similar m/z values. Analogous resonances are expected whenever the sample is a heterogeneous mixture assembled from a common building block.

Dynamic Calibration Enables High-Accuracy Charge Measurements on Individual Ions for Charge Detection Mass Spectrometry.

Charge detection mass spectrometry (CDMS) depends on the measurement of the charge induced on a cylinder by individual ions by means of a charge-sensitive amplifier. For high-accuracy charge measurements, the detection cylinder is embedded in an electrostatic linear ion trap (ELIT), and the ions oscillate back and forth through the cylinder so that multiple measurements are made. To assign the charge state with a low error rate, the charge of each ion must be determined with an uncertainty (root-mean-square deviation) of around 0.2 elementary charges. We show here that high-accuracy charge measurements can be achieved for large ions by dynamic calibration of the charge measurement using an internal standard. The internal standard is generated by irradiating the detection cylinder, by means of a small antenna, with a radiofrequency signal. Using this approach, we have obtained a relative charge uncertainty of around 5 × 10-4, allowing charge-state resolution to be achieved for single ions with up to 500 charges. In another application of this approach, the detection cylinder is irradiated with a signal that counteracts the transients generated when the potentials on the ELIT end-caps are switched to trapping mode. Using this approach, the dead time after switching (during which the signal cannot be analyzed) has been reduced by more than an order of magnitude. With charge-state resolution for ions with up to 500 charges, we were able to calibrate the charges precisely. The results show that the response of the charge-sensitive amplifier with dynamic calibration is linear to within a small fraction of an elementary charge.

Charge Detection Mass Spectrometry Measurements of Exosomes and other Extracellular Particles Enriched from Bovine Milk.

The masses of particles in a bovine milk extracellular vesicle (EV) preparation enriched for exosomes were directly determined for the first time by charge detection mass spectrometry (CDMS). In CDMS, both the mass-to-charge ratio (m/z) and z are determined simultaneously for individual particles, enabling mass determinations for particles that are far beyond the mass limit (∼1.0 MDa) of conventional mass spectrometry (MS). Particle masses and charges span a wide range from m ∼ 2 to ∼90 MDa and z ∼ 50 to ∼1300 e (elementary charges) and are highly dependent upon the conditions used to extract and isolate the EVs. EV particles span a continuum of masses, reflecting the highly heterogeneous nature of these samples. However, evidence for unique populations of particles is obtained from correlation of the charges and masses. An analysis that uses a two-dimensional Gaussian model, provides evidence for six families of particles, four of which having masses in the range expected for exosomes. Complementary proteomics measurements and electron microscopy (EM) imaging are used to further characterize the EVs and confirm that these samples have been enriched in exosomes. The ability to characterize such extremely heterogeneous mixtures of large particles with rapid, sensitive, and high-resolution MS techniques is critical to ongoing analytical efforts to separate and purify exosomes and exosome subpopulations. Direct measurement of each particle's mass and charge is a new means of characterizing the physical and chemical properties of exosomes and other EVs.

Dramatic Improvement in Sensitivity with Pulsed Mode Charge Detection Mass Spectrometry.

Charge detection mass spectrometry (CDMS) is emerging as a valuable tool to determine mass distributions for heterogeneous and high-mass samples. It is a single-particle technique where masses are determined for individual ions from simultaneous measurements of their mass-to-charge ratio (m/z) and charge. Ions are trapped in an electrostatic linear ion trap (ELIT) and oscillate back and forth through a detection cylinder. The trap is open and able to trap ions for a small fraction of the total measurement time so most of the ions (>99.8%) in a continuous ion beam are lost. Here, we implement an ion storage scheme where ions are accumulated and stored in a hexapole and then injected into the ELIT at the right time for them to be trapped. This pulsed mode of operation increases the sensitivity of CDMS by more than 2 orders of magnitude, which allows much lower titer samples to be analyzed. A limit of detection of 3.3 × 108 particles/mL was obtained for hepatitis B virus T = 4 capsids with a 1.3 µL sample. The hexapole where the ions are accumulated and stored is a significant distance from the ion trap so ions are dispersed in time by their m/z values as they travel between the hexapole and the ELIT. By varying the delay time between ion release and trapping, different windows of m/z values can be trapped.

Accumulation of metals and polycyclic aromatic hydrocarbons in agricultural soil after additions of street sediment in southern Ontario.

Prior to 2012 street sediment from the Greater Toronto Area was being managed by a local authority and provided to rural landowners under the assumption it was clean fill. The aim of this study was to characterise the chemical and physical composition of that street sediment applied to an agricultural field in southwestern Ontario, Canada and determine if contaminants had migrated to native soil. Soil was sampled from an impact and a background location during the fall of 2016 at four soil depths (0-10, 10-20, 20-30 and 30-40 cm below the surface) to characterise texture, pH, organic content, recoverable metals and total polycyclic aromatic hydrocarbons (PAHs). Textural analysis revealed street sediment was dominated by very coarse and coarse sand which differed from the native silty clay loam and extended to 30 cm below the surface. Some PAHs, including benzo(a)pyrene (1.29 µg g-1) exceeded the typical regional background concentrations. A distinct pattern of high molecular mass PAHs in the native soil below street sediments suggests that PAHs have migrated to native soil. To our knowledge this is the first study to report PAH concentrations in street sediment in Ontario and to show their potential movement and introduction to native soil. Future studies should focus on transport mechanisms and understanding movement of PAHs in native coarse textured soil.

Evaluation of a Passive Sampling Method for Long-Term Continuous Monitoring of Volatile Organic Compounds in Urban Environments.

Environmental Protection Agency Method 325 was developed for continuous passive monitoring of volatile organic compounds (VOCs), particularly benzene, at petroleum refinery fencelines. In this work, a modified version of the method was evaluated at an Ontario near-road research station in winter to assess its suitability for urban air quality monitoring. Samples were collected at 24 hour and 14 day resolution to investigate accuracy for different exposure times. Tubes were analyzed by thermal desorption-gas chromatography-mass spectrometry, and 11 VOCs were quantified, including aromatic air toxics. The same VOCs were simultaneously monitored using traditional canister sampling for comparison, and a subset of four were also monitored using a novel miniature gas chromatograph. Good agreement (within 10%) was observed between the 14 day passive tube samples and the canister samples for benzene. However, field-calibrated uptake rates were required to correct passive tube concentrations for less volatile aromatics. Passive tube deployment and analysis is inexpensive; sampling does not require power, and accurate measurements of benzene are demonstrated here for an urban environment. The method is expected to be advantageous for the generation of long-term continuous benzene datasets suitable for epidemiological research with greater spatial coverage than is currently available using traditional monitoring techniques.

Probability of foliar injury for Acer sp. based on foliar fluoride concentrations.

Fluoride is considered one of the most phytotoxic elements to plants, and indicative fluoride injury has been associated over a wide range of foliar fluoride concentrations. The aim of this study was to determine the probability of indicative foliar fluoride injury based on Acer sp. foliar fluoride concentrations using a logistic regression model. Foliage from Acer nedundo, Acer saccharinum, Acer saccharum and Acer platanoides was collected along a distance gradient from three separate brick manufacturing facilities in southern Ontario as part of a long-term monitoring programme between 1995 and 2014. Hydrogen fluoride is the major emission source associated with the manufacturing facilities resulting with highly elevated foliar fluoride close to the facilities and decreasing with distance. Consistent with other studies, indicative fluoride injury was observed over a wide range of foliar concentrations (9.9-480.0 µg F- g-1). The logistic regression model was statistically significant for the Acer sp. group, A. negundo and A. saccharinum; consequently, A. negundo being the most sensitive species among the group. In addition, A. saccharum and A. platanoides were not statistically significant within the model. We are unaware of published foliar fluoride values for Acer sp. within Canada, and this research provides policy maker and scientist with probabilities of indicative foliar injury for common urban Acer sp. trees that can help guide decisions about emissions controls. Further research should focus on mechanisms driving indicative fluoride injury over wide ranging foliar fluoride concentrations and help determine foliar fluoride thresholds for damage.

Ultra-trace level speciated isotope dilution measurement of Cr(VI) using ion chromatography tandem mass spectrometry in environmental waters.

The reliable analysis of highly toxic hexavalent chromium, Cr(VI), at ultra-trace levels remains challenging, given its easy conversion to non-toxic trivalent chromium. This work demonstrates a novel analytical method to quantify Cr(VI) at low ngL(-1) concentration levels in environmental water samples by using speciated isotope dilution (SID) analysis and double-spiking with Cr(III) and Cr(VI) enriched for different isotopes. Ion chromatography tandem mass spectrometry (IC-MS/MS) was used for the analysis of Cr(VI) as HCrO4(-) → CrO3(-). Whereas the classical linear multipoint calibration (MPC) curve approach obtained a method detection limit (MDL) of 7ngL(-1) Cr(VI), the modified SID-MS method adapted from U. S. EPA 6800 allowed for the quantification of Cr(VI) with an MDL of 2ngL(-1) and provided results corrected for Cr(VI) loss occurred after sample collection. The adapted SID-MS approach proved to yield more accurate and precise results than the MPC method, allowed for compensation of Cr(VI) reduction during sample transportation and storage while eliminating the need for frequent external calibration. The developed method is a complementary tool to routinely used inductively-coupled plasma (ICP) MS and circumvents typically experienced interferences.

How we transitioned to a comprehensive professional and graduate student affairs office.

BACKGROUND: Contemporary student affairs units arm students with professional skills, abilities and dispositions as they promote student learning, growth and development, as opposed to providing only administrative services. AIM: To describe the process for designing, planning, implementing and assessing a comprehensive student affairs unit that serves graduate and professional students at the University of North Carolina at Chapel Hill Eshelman School of Pharmacy. METHOD: A student services office that served only professional students was transformed in 2011 to an office of student affairs. The goal of the expanded, comprehensive unit is to work, in collaboration with academic affairs, to promote holistic student growth and development through proactive, intentional planning of co-curricular experiences. RESULTS: The comprehensive student affairs model has allowed for more student programming and mentoring opportunities, improved graduate students' feelings of connectedness to the School and improved efficiency of processes. The next steps include thorough assessment of the model and monitoring of the strategic plan. CONCLUSIONS: A comprehensive, centralized student affairs unit, working in partnership with academic affairs, can help professional and graduate health affairs programs meet their goals for student development, while improving the efficiency of administrative processes. This model can be easily implemented in other schools.

Warm season chloride concentrations in stream habitats of freshwater mussel species at risk.

Warm season (May-October) chloride concentrations were assessed in stream habitats of freshwater mussel species at risk in southern Ontario, Canada. Significant increases in concentrations were observed at 96% of 24 long-term (1975-2009) monitoring sites. Concentrations were described as a function of road density indicating an anthropogenic source of chloride. Linear regression showed that 36% of the variation of concentrations was explained by road salt use by the provincial transportation ministry. Results suggest that long-term road salt use and retention is contributing to a gradual increase in baseline chloride concentrations in at risk mussel habitats. Exposure of sensitive mussel larvae (glochidia) to increasing chloride concentrations may affect recruitment to at risk mussel populations.

Spatial and seasonal variations in atrazine and metolachlor surface water concentrations in Ontario (Canada) using ELISA.

Concerns regarding the impacts of pesticides on aquatic species and drinking water sources have increased demands on water quality monitoring programs; however the costs of sample analysis can be prohibitive. In this study we investigated enzyme-linked immunosorbent assay (ELISA) as a cost-effective, high through-put method for measuring pesticide concentrations in surface waters. Seven hundred and thirty-nine samples from 158 locations throughout Ontario were analysed for atrazine and metolachlor from April to October 2007. Concentrations ranged from <0.1 to 3.91 µg L(-1) (median=0.12 µg L(-1)) for atrazine and from <0.1 to 1.83 µg L(-1) (median=0.09 µg L(-1)) for metolachlor. Peak concentrations occurred in late spring/early summer, in rural agricultural locations, and decreased over the remainder of the growing season for both herbicides. About 3% of the samples that had ELISA results occurring above the limit of quantification (0.10 µg L(-1)) were evaluated against gas chromatography-mass spectrometry (GC-MS). Linear regression analysis revealed a R(2) value of 0.88 and 0.39, for atrazine and metolachlor, respectively. ELISA tended to overestimate concentrations for atrazine and metolachlor, most likely because the ELISA kits also detect their metabolites. Atrazine data suggest that ELISA may be used complementary with GC-MS analysis to enhance the spatial and temporal resolution of a water quality monitoring study. The commercially available metolachlor ELISA kit requires further investigation. ELISA may be used to detect atrazine and metolachlor in surface water samples, but it is not recommended as a quantitative replacement for traditional analytical methods.

Low cost monitoring of glyphosate in surface waters using the ELISA method: an evaluation.

Concerns have been raised in the scientific community regarding the environmental implications of a dramatic increase in corn-based ethanol production and associated increases in pesticide use. The use of glyphosate, a broad-spectrum herbicide, for corn production has increased considerably in recent years in Canada and the United States. The cost of measuring concentrations of organic contaminants in the environment using traditional wet chemistry methods can be prohibitive; especiallywhen large numbers of samples are required to quantify the spatial and temporal variability in contaminant concentrations. The goal of our study was to evaluate a cost-effective method to measure glyphosate concentrations in surface waters. The reliability of enzyme-linked immunosorbent assay (ELISA) results was evaluated against liquid chromatography tandem mass spectrometry, and linear regression results for 30 water samples from urban watersheds revealed a strong relationship (R2 = 0.88). These results suggest that ELISA methods, used in conjunction with traditional methods, represent a cost-effective approach to enhance the spatial and temporal resolution of a water quality monitoring study. Additionally, we measured a total of 739 surface water samples from over 150 sampling locations throughout Ontario using ELISA from April to October 2007. Concentrations exceeded the method detection limit of 0.1 microg/L in 33% of the samples, with a maximum concentration of 12.0 microg/L. Glyphosate showed a bimodal temporal distribution with peak concentrations occurring in late spring/early summer and fall, and did not exceed the Canadian Council of Ministers of the Environment (CCME) guideline for the protection of aquatic life (65 microg/L) in any of the samples.